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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Breeding of European Bee-eaters Merops apiaster in former sea dikes at the German North Sea coast
Auteurs :	Thorsten Krueger, Auteur ; Matthias Bergmann, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (135(4) 2015)
Article en page(s) :	151-166
Résumé :	In the course of a strong influx of European Bee-eaters in northern West, Central and East Europe on 11th June 2015 a flock of 18-20 individuals was discovered at the East Frisian/North Sea coast (midpoint at about 53 40' N, 7 degrees 33' E; Lower Saxony). Thus, the birds were present in the sea marsh, a landscape naturally not providing sandy walls or similar structures for the construction of nesting burrows. But the Bee-eaters had discovered a site with open soil and a low wall in a former sea dike (a so called "sleeper dike") of the third dike line and started to dig nesting burrows. The site was created by cattle, which graze on the dike and which had ruined the sod over years. Since this site had space only for three breeding pairs, the remaining birds spread to six other sandy sites, which were situated also in the third dike line and in another (second) dike line. In this way the birds formed a loose colony of nine pairs in total in an area of 1.2 km(2) (mean distance among nest sites: 1,117 m). The breeding walls were on average 611 cm wide and measured 79 cm at their highest points. The mean distance of the breeding burrows to the top of the dike was 171 cm, the mean height above the ground was 34 cm and the distance to the top of the breeding wall 39 cm. The mean length of the breeding burrows was 96 cm.The two dikes are 200 and 250 years old and represent very old grassland continuously used as pastures. Due to the large variety of plant species the old dikes are very rich in insects and represent hotspots of biodiversity surrounded by a marsh landscape which is intensively farmed, homogeneous and comparatively species-poor. In addition to the presence of open and sandy sites with walls this could have been a key factor for the settlement of the Bee-eaters. Apart from two broods destroyed by cattle all the other broods were successful, although the weather was very wet, windy and cold for several days each in the course of the breeding season. We attribute the positive result to a good food supply primarily bumblebees and bees were caught which was supplemented especially on days with heavy rainfall through the use of some bee hives in the area.The records represent the northwesternmost breeding site in Germany so far. It is described in detail. Further, possible causes for the occurrence, the extraordinary breeding sites and the ecological value of historic dikes resp. sleeper dikes and their importance for nature conservation are discussed.

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